Answer :
Area = length x width
21 = (2w-1)w
21 = 2w^2 -w
2W^2 - w -21=0
(2w-7 )(W +3)=0
2W-7=0 or w+3=0
W=7/2 or w=-3
Width cannot be negative.
So width is 7/2=3.5
Then the length is 6
21 = (2w-1)w
21 = 2w^2 -w
2W^2 - w -21=0
(2w-7 )(W +3)=0
2W-7=0 or w+3=0
W=7/2 or w=-3
Width cannot be negative.
So width is 7/2=3.5
Then the length is 6